I'm not positive about this and I may be misquoting a figure here since I'm used to my HCH and not the Prius, but I believe the maximum FE gained from P&G is at a max 41 miles per hour and a min 22 MPH, based on RPMs used during the Pulse phase over the amount of time to cap back at 41 MPH and the distance gained during the recurring Glide. I think.